Drill



Nov. 8, 1932. i EMM 1,887,374

DRILL Filed April 10. 1929 C9 INVENTOR.

J'oszbh vcfmmons ATTORNEYS m ma Nov. 8,1932

UNITED STATES PATENT orrlca V. IONS, 0! mm HEIGHTS VILLAGE, OHIO, ABSIGNOB 'I'O m CLEVE- LAND TWIST DRILL comm, OI CLEVELAND, OHIO, A CORPORATION 01' OHIO .nmr.

Application ma April 10, me. Serial so. erases.

The present invention, relating, as indicated, to drills, has more articular reference to drills of the type whic are provided with a cutter consisting of a. hard metal alloy or 6 the like, and its primary object, broadly stat ed, is to improve the construction of such drills to the end of better adapting them to the characteristics of the material of which their cutters are com osed.

-0 It is well recognize that the extreme hardness' of the so-called hard metal alloys should well adapt them to being used as the cutting members of tools of the general class referred to, but it must also be reco ized that in tools which have employed suc materials for the indicated purpose, the expected advantages have not a ways been fully obtained. I have investigated this apparent failure of such tools to realize the ex cted improvements in cutting efliciency an have found that the present constructions are objectionable in two respects; in the first lace, such constructions do not provide su cient strength to enable a complete-utilization of the potentially very large cutting abilities of the material oftheir working parts, and in the second place, in such constructions there is a tendency for the working parts to chip and crumble; These features of present tools 80 which employ cutting members made of the hard metal alloys are, I believe, due on the one hand to the fact that the actual hardness and cutting ability of such materials has not been fully appreciated, and on the other hand to the fact that their sometimes inadequate toughness and strength have not been taken into account. In other words, it has been discovered that these attempted uses of the hard metal alloys have failed to afford the expected increased efiiciency for the reason that they did not provide the means of completely utilizing their desirable and advantageous hardness, and for the further rea-- son that they did not provide the means of compensating for their undesirable and disadvantageous brittleness and'lack of toughness and strength. l

My invention, with a view to correcting the above-mentioned and objectionable features of present drill constructions, concontemplated. In the case of large drills with templates certain improvements whereby strength suflicient to enable a more complete utilization of the cuttin abilities of the hard metal alloys will be a orded', and whereb the sometimes inadequate strength and lac of toughness or even brittleness of such materials will be effectively compensated for. In obtaining the first of these im rovements, the usual practice is departed rom in that a shorter operating portion with narrower flutes and a thicker web is rovided, and in obtainin the second of suc improvements, a reduction in the ma itude of the helix angles of the active sur aces of such flutes is 05 a diameter of about two inches, the length of the flutes will be, say, four or fewer times a the diameter of the operating portion, and in the case of small drills when a diameter of about one-eighth of an inch, the length of such flutes Wlll be, say, eight or fewer times the diameter of the operating portion. Similarly, the width of the flutes will be less than say, eighty degrees of the circumference of the operating portion, and the thickness of 7 the web between such flutes will be greater than, say, twenty per cent. of the diameter of the operating portion. correspondingly, and for the purpose of co ensating for the deficient pro erties of the ard' metal alloy 30 cutting mem ers, it is intended that ordinarily the helix angles of the active surfaces of the flutes formed in the operating portion shall be between, say, minus ten degrees and plus twenty-two degrees and of substantially unlform magnitude at all pointslongitudinally, but in. cases, it is contemplated that even 1n the same tool such an les shall vary if a variation is necessary toa ord .the deslred compensation and to, at the same time, provide an adequate hole-clearing capacity for the sections of the flutes to the rear of those sections contiguous to the cutting end.

To the accomplishment of the foregoing and related ends, said invention then, consists of the means hereinafter fully described and particularly pointed out in the claims. The annexed drawing and the followingde' scription set forth in detail certain structure embodying the invention, such; disclosed means constituting, however, but one of vari- 4 5 and transverse sectional views of a twist I AU drill which embodies the present improvements; and Fig. 4: is a side elevational view of a modification of the drill shown in the preceding figures.

The'drill illustrated in Figs. 1, 2 and 3, consists of a shank 10, an operating portion 11, and an inserted or attached cutter 12. The shank and the operating portion 11 may be constituted of any suitable material, of tool steel, for example; and the cutter '12 may be constituted of one or another of the so-called hard metal alloys, compounds or compositions, of one conslsting of a cemented carbide of tungsten or molybdenum, for example. Such cutter is secured (as by welding or brazing) within a slot formed in the end of the operatin portion 11, and its edges 13 and 14 are pre erably arran ed for effecting most of the cutting, the e ges 15 of such operating portion functioning either as guides or as supplementary cutters or scrapers.

In accordance with this invention: in large 0 sized drills having a diameter of, say, two

inches, it is contemplated that the length of the flutes 16 in the operating portion 11, that is to say the distance A, shall be something like four or fewer times the magnitude of the diameter B; and in drills of the smaller sizes, of say, one-eighth of an inch in diameter, it is contemplated that the distance A shall he, say, eight or fewer times the magnitude of the diameter B. Similarliy, my in- 4o vention contemplates that the 'wi th of the flutes 16, when measured on the circumference, that is to say the magnitude C, shall be less than, say, eighty degrees, and with the same object in View, it is contemplated that the magnitude D, that is to say the thickness of the web, shall be more than, say, twenty per cent. of the diameter B. If desired, however, such web thickness may be reduced in the usual manner at the end in order to facilitate feeding when the tool is in use.

The above-discussed dimensional characteristics, or the thickness of the web, width of the flutes, andlength of the flutes, are made desirable by the potentially large cutting capabilities of the materials of which the insert 12 is composed, but in constructing a drill to fully utilize these capabilities, it must be recognized that some of such materials while advantageously hard are nevertheless lacking in toughness and strength. Therefore, and with the obj ect of compensating for 'these deficiencies, my invention intends that the helix angles of the active surfaces 17 of the flutes 16, which surfaces are continued on the insert 12, shall be between minus ten degrees and plus twenty-two degrees these values having been found to effectively overcome a tendency for the material of the cutting insert to chip and crumble.

In the particular drill shown in Figs. 1, 2 and 3, the helix angle E is tendegrees, the dimension D is twenty-eight per cent. of the .dimension B, the dimension A is three times the dimension B, and the dimension C is sixty-five degrees.

In some cases, the helix angle of those ortions of the active surfaces of. the flutes w ich are formed on the cutting insert may advantageously differ from the helix angle of those portions of such surfaces which are formed on the operatin portion. The drill illustrated in Fig.4 as an operating portion 20 which is provided with the flutes 21 and the cutting insert 22. -The helix angle of those portions of the active surfaces of such flutes which are formed on such operating portion is about ten degrees, and in contrast, the helix angle of those portions of such surfaces whichare formed on the cuttin insertare parallel with the axis of the too This arrangement provides for the flutes having a suflicient twist to carry the cuttings out of the hole being drilled and afl'ords such a degree of angularity to the cutting lips 23 that the material of which such lips are constituted will have little if any tendency to chip or crumble. The amount of this variation in the angularity of the different parts of the active or o erating surfaces of the flutes will, of course, epend upon the size of the drill and the conditions of its use, in some cases such variation will be greater and in others less than ten degrees.

The operating ends of the drills herein illustrated and described may be ground for use in any desired manner, but the angle of lip clearance, the included angle of the point,

and the other features of the ends so ground should preferably be such as not to materially offset the advantages obtained in the manner above explained. It will be understood that my invention contemplates the use of other than tool steel for the main part of the operating portion, that different methods of attaching .the hard metal cutter or cuttersmay be employed, and that in cases the entire operating portion of the tool may be constitutaad of the material desired in the cutting en Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the structure herein disclosed, provided the means stated'by any of the following claims 'or the equivalent of such stated means be employed.

I therefore particularly point out and dis- I tinctly claim as my invention and havin flutes with active edges of helix angles ofetween and 0.

3. As a new article-of manufacture a-com- :posite metal-working drill having in its oper.

at'ing end a cutter of tungsten carbide, andhaving a helix angle presenting a negative porting said cutting-blade against breaka e rake. a v

4. As a new article of-manufacture, acomposite metal-working drill having in'its operating end a cutterof tungstencarbide, and

flutes whose act'ive edges adjacent the cutter end have helix angles-of from- 10 to-0 and whose active edgesimore remote have helix, angles of'b'etween 0-" -and +229. I

5. As afnew .article of manufacture, a

degrees and positive22 degrees.- I

- 10.- A rotary metalcutting drill of great strength and rigidity havin an operatin portiongformed with two he ical flutes ail having a helix angleof between minus mtermediatelands, said flutes having a width of less than 68- degrees of the circumference and a depth so that the web thickness of the drill at a'section one-half diameter from the point is more than 20'jper cent of the diameter of the drill, said flutes andlands having a' helix an le of between minus 10 degree'sjand,

' his 22 egrees, and saidop'erat'ing portion a'ving-primary cutting edges of hard non metal-working drill having an end cuttingblade of a frangible hard non-ferrous allo and'means for supporting said cutting-bla e against breakage, said means including steel shoulders backing the cutting-blade and thence extending generally axially as secondary cuttin edges and providing flutes of arcuate wi th less than 68.

'6. 'As a new article ofv manufacture, a

metal-working drill having an :end cuttingblade of tungsten carbide, and means forisup-.

said means including steel shoulders bac ing the cutting-blade and thence extending generally axially as secondary cuttin edges and providing flutes of arcuate wi th' less than 68.

'7. As a new article of manufacture, a metal-working drill having an end cutting-' blade of a frangible hard non-ferrous allog, and means for supporting said cutting-bla e against breakage, said means including steel shoulders backing the cutting-blade and I thence extending generally axially as secondwith helix ary cuttin edges and having flutes angles of tween'-1 0 and +22.

8. As 'a new article of manufacture, a metalworking drill having an end cutting-' blade of tungsten carbide, and means for supporting said cutting-blade against breakage, said means including steel'sh'oulders backing the cutting-blade and thence extending generally axially as secondary cutting edges and having flutes with helix angles of between 10 and +22.

9. A rotary metal cutting drill of great ferrous material. 1 Sgned'by me this-8th .da of April, 1929; JOSEPH EMMONS.

strength and rigidity having an operatin portion formed with two helical flutes an intermediate lands, said flutes having a width of less than 68 degrees of the circumference and a depth so that the web thickness of the drill at a section one-half diameter from the point is more than 20 per cent of the diameter of the drill and said flutes and lands 

